This allergic sensitivity of specific persons to the material has become a major problem in the health care industry and solutions are needed to prevent health care institutes from switching to inferior synthetic alternatives.
Some solutions have been proposed which denature the allergens. These methods mostly use added stabilizers to keep the rubber particles of the NRL from clogging. This changes the surface properties of the suspended rubber particles, resulting in different mechanical properties of the material. Other methods include washing finished latex products in aqueous solutions to remove surface proteins. None of the existing methods is able to completely prevent allergens to leach from latex products when they are immersed in water: all methods show detectable amounts of leachable allergens.
This invention thus relates to products made of natural rubber latex (NRL) that come into contact with humans and especially to NRL that exhibits no detectable amount of leachable allergens (and therefore or at least strongly reduced allergenicity potential) without the loss of physical properties or the introduction of new components altering the NRL formulation.
Solutions have been found in denaturing the allergens in the natural rubber latex suspension using proteases, strong oxidatives and bases. One of the major drawbacks of denaturing the proteins and allergens in the latex suspension is that the stabilizing function of these proteins is lost with it as well. This problem can be solved by adding stabilizers, but these will be present in the product after drying affecting the physical and mechanical properties of the NRL product. This invention therefore focuses on treatment of the NRL product after its production process.
The use of proteases in the latex suspension (JP9071604, JP2003020301, JP2001081107, JP2000109596, US20020091232) results in a lowered allergen content. However, a problem with these prior art solutions is, that these do not provide a sufficient solution to the problem of preventing allergic reactions in sensitized people that come into physical contact with NRL. Another disadvantage is that proteases themselves are known to be a source of allergic reactions, so care must be taken to completely remove the proteases from the final product and care should be taken while working with these proteases.
The oxidative washes (US20020103333, U.S. Pat. No. 5,910,567) generally use a strong chlorine or hypochlorite wash, which is able to reduce the leaching of allergens from NRL upon contact with water. However, in case the oxidator concentration is too strong, the NRL is affected by this wash, resulting in diminished gripping, elastomeric and tactile properties. In general the product becomes stiff, exhibiting hysteresis and requiring a heavy load to stretch. In case of a glove, the result is a poor fit and fatigue during use. These problems can be countered by using an additive to the NRL formulation that opposes these effects (US2002103333), but the material and its mechanical properties are still different from regular NRL. No cases have been reported where the NRL itself is not affected in a negative way by an oxidative wash (by choosing mild oxidation conditions) and wherein no detectable amounts of leachable allergens are found to remain after such a known treatment. The leachable allergen levels are in these prior art documents lowered, but still remain to be detectable.
The use of chemical proteolysis (DE4406584) by increasing the pH in the latex suspension is another option to remove the allergenicity. Experiments using this treatment resulted in products with inferior mechanical properties and poor processability into NRL products. Drying of the product took longer and the product could easily be torn apart by stretching.
It is acknowledged that some proposed procedures apply the use of an alkaline wash to remove proteins (JP9071604, JP2003020301, US20020103333). The focus of this wash is actually only to remove or modify the structure of the protein, and not to destroy the primary structure of the proteins. The conditions used for these washing steps are considered too mild to be considered an embodiment of chemically proteolysing the peptide bonds of the proteins. Moreover, in all these prior art disclosures, no decrease to undetectable amounts of leachable allergens is known to have been reported.
Further it is noted here that the state of the art, as acknowledged herein, comprises the disclosures of U.S. Pat No. 5,910,567; and GB-2.366.509. These disclosures all relate to treatment of natural rubber latex products to reduce allergenicity thereof. For instance according to U.S. Pat. No. 5,910,567 an alkaline solution at temperatures between room temperature (20° C.) and below 98° C. is used to wash NLR products to reduce allergenicity thereof. In GB-2.366.509 also NLR products are washed in an alkaline solution, after having been powdered with cornstarch and immersed in water heated to a temperature between 80° C. and 98° C. and removed from the water. After the hot water wash, according to this disclosure, the NLR products are subjected to the alkaline solution at an undisclosed temperature.
Thus the prior art teachings lead the skilled person to the belief that with the temperatures according to the prior art teachings a sufficient result, if not the best possible result, was obtained. Notwithstanding the fact, that many possible solutions have hitherto been presented, and the belief of the skilled artisan of already having available the optimal technology, no fully satisfactory solution has been made available in the relevant technical field to more substantially reduce the allergen levels, preferable to practically undetectable levels (at least: undetectable with currently available and commonly employed testing methods), while maintaining the desired properties of the NRL products.